| Preparation of natural rubber (NR) latex/low density polyethylene (LDPE) blown film and its properties | |
| Mahapram S., Poompradub S. | |
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| Abstract | |
| Heat-shrink composite films based on LDPE and NR latex blends were prepared. The effect of varying the NR latex content on the physical, mechanical and dynamic properties and the heat-shrinkability of the composite films were investigated. The addition of NR latex into the LDPE films at up to 7.5 phr did not affect the clarity of the film but affected the color due to the β-carotene content of the NR latex. The degree of crystallinity of the LDPE/NR composite films increased with increasing NR latex content up to 7.5 phr, as did the tear strength and impact resistance up to a NR latex content of 5 phr. However, the tensile strength and hardness of the LDPE/NR composite films decreased with increasing NR latex content. The heat-shrinkability of LDPE films was improved by adding NR latex. A mechanism for the strain-induced crystallization of the LDPE/NR composite films during the blown film process is proposed. © 2011 Elsevier Ltd. All rights reserved. | |
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| Blown-films; Degree of crystallinity; Dynamic property; LDPE film; Natural rubbers; NR; NR latex; Shrinkability; Straininduced crystallization; Tear strength; Composite films; Hardness; Impact resistance; Impact strength; Latexes; Polymer films; Rubber films; Tensile strength; Film preparation | |
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| Introducing surface-tethered poly(acrylic acid) brushes as 3D functional thin film for biosensing applications | |
| Akkahat P., Hoven V.P. | |
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| Abstract | |
| Carboxyl groups of surface-tethered poly(acrylic acid) (PAA) brushes should be able to serve as versatile moieties for a wide range of chemical modifications, including an attachment of bioactive species that can act as sensing probes for biosensors. In this research, poly(tert-butyl acrylate) (P. t-BA) brushes were prepared by surface-initiated atom transfer radical polymerization of tert-butyl acrylate. PAA brushes were then obtained after removal of the tert-butyl groups from the P. t-BA brushes by acid hydrolysis. The carboxyl group density of the PAA brushes can be varied as a function of chain length or molecular weight. The reactivity of the carboxyl groups of PAA brushes towards the immobilization of biotin, a frequently used model bioactive probe in biosensing applications, was evaluated. Qualitative determination of streptavidin (SA) binding to the biotin-attached PAA brushes was verified by fluorescence microscopy. The efficiency of the PAA brushes to act as a three dimensional (3D) precursor layer for biosensing applications was further demonstrated using surface plasmon resonance (SPR), where the biotin-attached PAA brushes showed an enhanced signal for the biospecific binding of SA in comparison with a self-assembled monolayer (SAM) of a carboxyl-terminated alkanethiol, used as a model two-dimensional (2D) conventional precursor layer. The PAA brushes showed very low non-specific interactions with two other tested proteins of a similar pI but different sizes. This desirable feature should be highly beneficial for the development of biosensors. © 2011 Elsevier B.V. | |
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| Biotin; Poly(acrylic acid); Polymer brushes; Streptavidin; Surface initiated polymerization; Acrylics; Biosensors; Carboxylic acids; Chemical modification; Coenzymes; Fluorescence microscopy; Free radical reactions; Hydrogels; Organic polymers; Polymerization; Probes; Self assembled monolayers; Surface plasmon resonance; Three dimensional; Three dimensional computer graphics; Two dimensional; Atom transfer radical polymerization; alkane; biotin; carboxyl group; poly(acrylic acid tert butyl ester); polyacrylic acid; polymer; streptavidin; thiol; unclassified drug; article; atom transfer radical polymerization; binding kinetics; biosensor; chemical modification; controlled study; fluorescence microscopy; hydrolysis; immobilization; molecular weight; priority journal; protein interaction; qualitative analysis; surface plasmon resonance; Acrylates; Biosensing Techniques; Biotin; Streptavidin | |
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| A new and efficient method for the synthesis of bromosilanes from hydrosilanes using Br3CCOOEt/PdCl2 as the catalyst | |
| Srithanakit P., Chavasiri W. | |
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| Abstract | |
| Bromosilanes were prepared conveniently and efficiently via the reaction of hydrosilanes and Br3CCOOEt in the presence of a catalytic amount of PdCl2 in refluxing THF over 15 min in high yields. The developed methodology was further applied for the one-pot synthesis of silyl ethers and silyl esters in excellent yields. © 2011 Elsevier Ltd. All rights reserved. | |
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| acetic acid derivative; bromosilane; ester derivative; ether; ethyl tribromoacetate; hydrosilane; silane derivative; silyl ester; unclassified drug; article; bromination; catalyst; chemical reaction kinetics; proton nuclear magnetic resonance; stoichiometry; synthesis | |
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| In situ silica reinforcement of methyl methacrylate grafted natural rubber by sol-gel process | |
| Watcharakul N., Poompradub S., Prasassarakich P. | |
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| Abstract | |
| In situ silica reinforcement of natural rubber (NR) grafted with methyl methacrylate (MMA) (MMA-GNR) was achieved via the sol-gel reaction of tetraethoxysilane (TEOS) by the use of solid rubber and latex solutions. Silica contents within the MMA-GNR as high as 48 and 19 phr were obtained when using the solid rubber and latex solutions, respectively, under optimum conditions. The conversion efficiency of TEOS to silica was close to 95%. The in situ formed silica MMA-GNR/NR composite vulcanizates were prepared. MMA-GNR/NR composite vulcanizates reinforced with the in situ formed silica prepared by either method had similar mechanical properties to each other, but a shorter cure time and higher mechanical properties than those reinforced with the commercial silica at 9 phr. The TEM micrographs confirmed that the in situ formed silica particles were well dispersed within the MMA-GNR/NR composite matrix, whilst the commercial silica particles showed a significant level of agglomeration and a lower level of dispersion. © Springer Science+Business Media, LLC 2011. | |
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| Composite matrices; Cure time; Grafted rubbers; In-situ; Methyl methacrylates; Natural rubbers; Optimum conditions; Silica content; Silica particles; Sol-Gel Reaction; Solid rubber; Tetraethoxysilanes; Vulcanizates; Well-dispersed; Acrylic monomers; Agglomeration; Conversion efficiency; Esters; Gels; Grafting (chemical); Latexes; Mechanical properties; Reinforcement; Rubber; Silica; Sol-gels; Solid solutions; Sols; Transmission electron microscopy; Sol-gel process | |
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| Aerobic oxidation of cyclic amines to lactams catalyzed by PVP-stabilized nanogold | |
| Preedasuriyachai P., Chavasiri W., Sakurai H. | |
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| Gold nanoclusters stabilized by poly(N-vinyl-2-pyrrolidone) (Au:PVP) are active and selective catalysts under aerobic conditions for oxidation of cyclic secondary amines at the -position of the nitrogen atom. The catalyst accelerates the formation of the imines by oxidation of the amines in aqueous solvent to afford the corresponding lactams. © Georg Thieme Verlag Stuttgart – New York. | |
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| 1,2,3,4 tetrahydroquinoline derivative; 1,2,3,4,5,6 hexahydro 1h benzo[b]azecine; 2,3,4,5 tetrahydro 1h benzo[b]azepine; alcohol; amine; cyclic amine; gold nanoparticle; lactam derivative; povidone; sodium hydroxide; solvent; tert butyl alcohol; unclassified drug; water; aromatization; article; catalyst; chemical reaction; chemical reaction kinetics; high temperature; oxidation; oxygenation; particle size; solubility; solvent effect; temperature sensitivity | |
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| Tuning hydrophobicity and water adhesion by electrospinning and silanization | |
| Pisuchpen T., Chaim-Ngoen N., Intasanta N., Supaphol P., Hoven V.P. | |
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| Electrospinning and silanization were synergistically employed to fabricate poly(vinyl alcohol) (PVA) and PVA/silica mixtures into flexible and chemically modifiable nanostructured surfaces with varying degrees of hydrophobicity and water adhesion. Surfaces possessing the greatest advancing water contact angle yet exhibiting a high level of water adhesion (θA/ θR ≈ 168°/0°) were achieved by the reaction of PVA fiber mats with multiple cycles of SiCl4/H2O treatment, followed by silanization with (1H,1H,2H,2H-perfluorooctyl)trichlorosilane. It is postulated that the strong pinning effect and hence the water adhesion originated from the collapse of the underlying fibrous structures and the removal of air pockets. The addition of silica to the PVA matrix improved the rigidity and thus prevented the fibers from collapsing, allowing air to remain trapped within the fibrous structure and giving the surface greater water repellency. Throughout the investigation, the three wetting models-Wenzel’s, Cassie-Baxter’s, and the Cassie-impregnating-were regularly referred to as a conceptual framework. The hydrophobic surface that exhibited strong water adhesion, or the so-called “Petal effect”, was elucidated in correlation with the fibrous structure of the film, as reviewed by microscopic analysis. In summary, electrospinning as a facile and cost-effective method provides promising opportunities for investigating the mechanistic character of nanowetting, nanoprinting, and nanocoating where the precise control of the dynamical three-phase contact line is of paramount importance. © 2011 American Chemical Society. | |
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| Air pockets; Conceptual frameworks; Cost-effective methods; Fibrous structures; Hydrophobic surfaces; matrix; Microscopic analysis; Nano-coatings; Nanoprinting; Nanostructured surface; Pinning effects; Precise control; PVA fiber; Silanizations; Three-phase contact line; Trichlorosilanes; Water contact angle; Water repellency; Wetting model; Contact angle; Electrospinning; Hydrophobicity; Magnetic bubbles; Silica; Surface chemistry; Surface structure; Adhesion | |
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| Enhancing antibacterial activity of chitosan surface by heterogeneous quaternization | |
| Vallapa N., Wiarachai O., Thongchul N., Pan J., Tangpasuthadol V., Kiatkamjornwong S., Hoven V.P. | |
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| This research aimed to increase the antibacterial activity of the chitosan surface by introducing quaternary ammonium groups via a heterogeneous two-step process: reductive alkylation using a series of different aldehydes followed by methylation with methyl iodide. ATR-FTIR and XPS analyses, together with water contact angle and zeta potential measurements, confirmed the success of the surface quaternization. The antibacterial activity of the surface-quaternized chitosan film against Staphylococcus aureus and Escherichia coli, as model Gram-positive and Gram-negative bacteria, respectively, were superior to that of the virgin chitosan film. The apparent damaged bacterial morphology upon contact with the surface-quaternized chitosan film was verified by SEM. Thus, the introduction of additional positive charges to the chitosan surface via the versatile and yet simple process of heterogeneous quaternization can significantly improve the antibacterial activity of the chitosan surface, especially in a neutral environment. © 2010 Elsevier Ltd. All rights reserved. | |
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| Anti-bacterial activity; ATR FTIR; Bacterial morphology; Chitosan film; Gram-negative bacteria; Methyl iodide; Neutral environment; Positive charges; Quaternary ammonium group; Quaternization; Reductive alkylation; SEM; Staphylococcus aureus; Surface modification; Two-step process; Water contact angle; XPS analysis; Zeta potential measurements; Aldehydes; Alkylation; Ammonium compounds; Bacteria; Bacteriology; Chitosan; Contact angle; Escherichia coli; Hydrophobicity; Polyethylenes; Zeta potential; Chitin; Bacteria (microorganisms); Escherichia coli; Negibacteria; Posibacteria; Staphylococcus aureus | |
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| Photocatalytic desulfurization of waste tire pyrolysis oil | |
| Trongkaew P., Utistham T., Reubroycharoen P., Hinchiranan N. | |
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| Waste tire pyrolysis oil has high potential to replace conventional fossil liquid fuels due to its high calorific heating value. However, the large amounts of sulfurous compounds in this oil hinders its application. Thus, the aim of this research was to investigate the possibility to apply the photo-assisted oxidation catalyzed by titanium dioxide (TiO2, Degussa P-25) to partially remove sulfurous compounds in the waste tire pyrolysis oil under milder reaction conditions without hydrogen consumption. A waste tire pyrolysis oil with 0.84% (w/w) of sulfurous content containing suspended TiO2 was irradiated by using a high-pressure mercury lamp for 7 h. The oxidized sulfur compounds were then migrated into the solvent-extraction phase. A maximum % sulfur removal of 43.6% was achieved when 7 g/L of TiO2 was loaded into a 1/4 (v/v) mixture of pyrolysis waste tire oil/acetonitrile at 50 °C in the presence of air. Chromatographic analysis confirmed that the photo-oxidized sulfurous compounds presented in the waste tire pyrolysis oil had higher polarity, which were readily dissolved and separated in distilled water. The properties of the photoxidized product were also reported and compared to those of crude oil. © 2011 by the authors. | |
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| Chromatographic analysis; Crude oil; Desulfurization; Mercury compounds; Oxidation; Oxides; Photooxidation; Solvent extraction; Sulfur; Sulfur compounds; Tires; Titanium; Titanium dioxide; Distilled water; High potential; High-pressure mercury lamp; Hydrogen consumption; ITS applications; Photo-catalytic; Reaction conditions; Waste tires; Pyrolysis | |
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| Styrene/acrylonitrile graft natural rubber as compatibilizer in rubber blends | |
| Angnanon S., Prasassarakich P., Hinchiranan N. | |
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| A graft copolymer of acrylonitrile (ACN) and styrene (ST) on natural rubber (NR) was prepared by solution polymerization initiated by benzoyl peroxide. The effect of graft NR (GNR) applied as a compatibilizer for NR/nitrile rubber (NBR) blends on their mechanical and physical properties was investigated. The results revealed that the tensile properties and oil-swelling resistance of the blends increased with increasing %graft copolymer of GNR. The tensile fracture surfaces of the compatibilized NR/NBR vulcanizates attested by scanning electron microscopy indicated the improvement of interfacial adhesion between two rubber phases. Moreover, the dynamic mechanical properties of compatibilized vulcanizates were also reported. © Taylor & Francis Group, LLC. | |
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| Acrylonitrile; Benzoyl peroxide; Dynamic mechanical property; Graft copolymerization; Interfacial adhesions; Mechanical and physical properties; Natural rubbers; Nitrile rubbers; Rubber blends; Rubber phasis; Solution polymerization; Styrene/acrylonitrile; Tensile fracture surfaces; Vulcanizates; Compatibilizers; Copolymerization; Cyanides; Graft copolymers; Grafting (chemical); Mechanical properties; Polymer blends; Scanning electron microscopy; Styrene; Tensile strength; Rubber | |
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